1. Field of the Invention
The present invention relates to an aluminum capacitor plate for use in electrolytic capacitors and a process for producing the same. More particularly, the present invenion relates to an aluminum capacitor plate having an enhanced capacitance, and to a process for producing such capacitor plates, wherein the term "aluminum" includes pure aluminum and aluminum-based alloys. Hereinafter the electrolytic capacitor will be referred to merely as capacitor.
2. Description of the Prior Art
In order to minimize the size of capacitors without trading off their ability it is essential to increase the capacitance of capacitor plates. To this end many proposals have been made; for example, one is to increase the surface area of the capacitor plates, and another is to form a film having a high dielectric constant on the plates, and a further proposal is to form a thin film of a dielectric substance.
In line with such demands in the industry the inventors have made inventions on aluminum capacitor plates, which are disclosed in Japanese Patent Publication (unexamined) No. 61-180420 and No. 61-214420. According to these inventions the surface of an aluminum capacitor plate is previously roughened, and vapor-plated with a particle-inclusive uneven film of titanium. As a result the roughness on the titanium film is doubled by the uneven profile of the aluminum substratum, thereby increasing the surface area of the capacitor plate, and enhancing the capacitance thereof.
Under the conventional titanium vapor-plating process an aluminum plate (foil) is subjected to titanium vapor while it travels between one roll and another within the vacuum Bell-jar. This process is especially adapted for mass production.
Nevertheless the capacitance achieved by the process mentioned above is not sufficiently high, and actually the process allows for an improvement. The inventors have pursued the study, and has completed the present invention by recognizing that the aluminum plate and the titanium film must have particular interrelated structures.